Hi Janibasha. Lots of great questions. I’ll try to provide high-level answers then provide some reading for you.
It looks like you’re still running Apcera CE. With CE, you have several types of VMs created based on answers you provide during the install, as follows:
- One is called “Orchestrator”. This VM provides all of the features and utilities to lifecycle manage the cluster (i.e. upgrade, patch, etc.). It’s a singleton, and you’ll never need to scale it more than just 1.
- Another is called “Central”. This VM in CE hosts many roles that are part of the Apcera cluster, such as the router, health manager, job manager, the API server, authentication services (for LDAP, Google OAuth, Keycloak, etc.), component DB, NATS server, etc. All of these roles can be scaled to provide high availability and to provide greater load capacity. Note that CE does not provide means to run more than one Central VM.
- The last is the “Instance Manager” VM, which is the container runtime host. It is the node that actually runs the containerized jobs/workloads. The more IMs you have, the more containers you can run. So this is the node type that you would install more of to increase scale.
For more information about the architecture and to learn about the various components, please visit this link:
One more note. In case you didn’t already know, last week Apcera released version 3.0 of the Apcera Platform. With this new release, Apcera is deviating from the CE product and making EE available to everyone. That means full enterprise features without any restrictions. With 3.0, you also get a ton of new features and enhancements. To read about what’s new in 3.0, please visit this link:
Apcera is 100% compatible with Docker, and is OCI compliant. That is, it can run Docker images. However, it does not run the Docker engine. Apcera uses its own container runtime/engine as it provides greater functionality and enables many of the unique features only found in the Apcera Platform. You could compare it to Kubernetes and Docker Swarm, and it has feature parity with those; however, Apcera provides even more features than even the latest release of those orchestration systems provide, especially with the 3.0 release.
Hope that helps!